RAIDZ Mirror - 1 disk has Bad GPT? How to fix easiest..?

[madgabz]

Hi, need some guidance from you RAID / ZFS moguls...
My 5-disk setup has a 2-disk zfs-mirror (ADA1+ADA2), which sometimes prevent the NAS from booting properly! It seems, the GPT is somehow at fault, though there are no more precise info than dmesg's last lines:

Code: Select all

GEOM: ada2: corrupt or invalid GPT detected.
GEOM: ada2: GPT rejected -- may not be recoverable.

AFAIK, this could be due to some old GEOM/regular software RAID, which was previously installed when these two enterprise-grade disks were used as a mirrored Windows boot/system-disk.
So, I've backed up all on the two drives, and am looking for a 'smart'/quick/easy way to fix the GPT/partition table erro. Can I somehow fix this while the drive is online, or can I just pull out the drive, wipe it entirely making sure the partition table is wiped too, then re-add the drive and let zfs rebuild?
Or, some 3rd suggestion?

Thanks in Advance..
Gabriel S. Hansen

[raulfg3]

If you use RAID5 is a normal warning message: http://wiki.nas4free.org/doku.php?id=faq:0047

I encourage you to use RaidZ1 instead.

[madgabz]

If you use RAID5 is a normal warning message: http://wiki.nas4free.org/doku.php?id=faq:0047

Ooohhh... Before asking for help here, I searched google, and only came up with two obscure links for NOT solving my problem lol... thanks for this, Raul!
After reading this, it's still not clear - to me, of course! - whether I should ignore this error or not.

I encourage you to use RaidZ1 instead.

As I stated - though admittedly, perhaps not clearly enough - the 2 disks ada1 + ada2 are in a RAIDZ-MIRROR, because i dont have any other disks of the same size for a 'proper' RAIDZ1 or 2 array. It's just two 160GB drives, mirrored for my music collection! I can go experiment as all is backed up, but just wanted to make sure that zfs will still rebuild a mirror, just like a striped set or raidz1, 2 or 3...

Thanks!

[fsbruva]

Part of raul's confusion is your terminology. The setup you have is just a zfs mirror. RAIDZ is usually used to describe a RAIDZ1 vdev with at least 3 drives.

Back to your question - yes, zfs will rebuild the mirror. But, this reslivering is a pretty disk intensive operation, takes some time, and you would be doing it twice.

Unless you are moving the bits via snail to retrieve from the backup, I would recommend a complete wipe of both drives and rebuild of the zfs pool. (Depending on the age of your hard drives, this might be relevant: viewtopic.php?f=59&t=1494 )

Since it is less than 160GB of data, I would go that way. When you create the pool, create separate datasets at the root of the pool, rather than folders. This will allow you to take snapshots of the root folders you care about (music, photos, video) on a separate basis, and it will increase the speed of your weekly zfs pool scrubs. (you are scrubbing on a regular basis, aren't you?)

[alexia90]

Thanks a lot, i was searching for this for very long time, I am so much glad to find this useful stuff.